Aqueous emulsion polymerization utilizing water-soluble salts of nu-dodecylbeta-alanine



United States Patent AQUEOUS EMULSION POLYMERIZATION UTILIZ- ING WATER-SOLUBLE SALTS OF N-DODECYL- BETA-ALANINE James R. Miller, Cuyahoga Falls, Ohio, B. F. Goodrich Company, New York, ration of New York assignor to The N. Y., a corpo- 5 Claims. (Cl. 26029.6)

The present invention relates to improvements in aqueous emulsion polymerization and pertains more particularly to improvements in the production of synthetic rubbers and resins by the polymerization of various monomeric materials in aqueous emulsion utilizing, as an emulsifying agent, a water-soluble salt of an N-alkyl-betaalanine.

Monomeric materials both monoolefinic and polyolefinic in nature, including vinyl compounds such as vinyl chloride, styrene, acrylate esters, etc, and also conjugated dienes such as butadiene-l,3, chloroprene, etc., have been polymerized in aqueous emulsion utilizing a wide variety of emulsifying and dispersing agents. Among the materials which have been used are colloidal protective materials such as bentonite clay, casein and starch derivatives, amino alcohols, polyvinyl alcohol and other hy drolyzed ester-type polymers; ordinary alkali soaps of fatty acids or rosin acids, various synthetic saponaceous materials such as the hymuolal sulfates and alkaryl sulfonates and other anionic emulsifiers; and aslo cationic emulsifiers such as the addition salts of primary alkyl amines such as lauryl amine hydrochloride and others. However, none of these emulsifying agents is entirely satisfactory as a general purpose emulsifier. One disadvantage is that it has been necessary to vary the emulsifier in changing from one monomer system to another and in changing from one catalyst system to another at difierent reaction temperatures. For example, in the preparation of general purpose butadiene styrene rubbers at temperatures of 35 to 50 C. the use of rosin acid soaps as emulsifiers produces polymers of excellent properties. When butadiene and styrene are polymerized at lower temperatures of to 10 C., however, so as to produce the so-called cold rubber" it has been found that the fatty acid soaps are preferable to rosin acid soaps. In contrast, fatty acid soaps are generally poor emulsifiers for emulsion polymerization of vinyl compounds since they yield emulsions or resin latices of relatively poor stability. Similarly, the other known emulsifying agents while advantageously used under certain conditions, possess marked disadvantages under other conditions.

I have now discovered that monomeric materials generally, including monoolefinic unsaturated compounds, are efliciently polymerized in an aqueous emulsion containing, as emulsifier, a water-soluble salt of an N alkyl substituted beta-alanine (a beta-amino propionic acid) in which an alkyl substituent group contains at least 8 carbon atoms, preferably from 10 to 25 carbon atoms, in a very short reaction time and with the production of exceedingly stable aqueous polymeric dispersions. The N-alkyl beta-alanines useful for this purpose have the general structure in which R is hydrogen or alkyl and R is an alkyl group of at least 8 carbon atoms. They are converted to useful anionic-type polymerization emulsifiers by reaction with an alkali such as sodium, potassium, lithium, or ammonium hydroxide or an organic base such as ethylamine, diethylamine or the like, and to useful cationictype emulsifiers by reaction with suitable mineral acids such as hydrochloric acid, and others which yield Watersoluble addition salts. Thus, the salts of N-alkyl betaalanines form a class of polymerization emulsifiers use ful over a very wide pH range from strongly acid to strongly alkaline, depending on the kind and amount of salt-forming reagent utilized.

The N-alkyl-beta-alanines may be produced by re action in solution between beta-propiolactone and a long chain alkyl amine. N-dodecyl-beta-alanine, for example, is made by separately dissolving beta-propiolactone and dodecylamine in acetonitrile, the solution of amine then being added gradually to the beta-propiolactone solution while maintaining the reaction mixture at a temperature of about 35" C. The white crystalline product obtained is then filtered and dried under vacuum to yield a product melting at 82 to 84 C. and analyzing 69.99% carbon, 11.84% hydrogen and 5.43% nitrogen Other N-alkylbeta-alanines are similarly made by substituting the proper alkyl amine for the dodecyl amine in the above illustration.

Illustrative compounds of the above class of N-alkyl beta-alanines include N-decyl-beta-alanine. N,N-didecylbeta-alanine, N-undecyl-beta-alaninc, N-dodecyl-betaalanine, N,N-didodecyl-beta-alanine, N-tridecyl-beta-ala nine, N tetradecyl-beta-alanine, N-pentadecyl-betaalanine, N,N-dipentadecyl-beta-alanine, N-hexadecyhbetaalanine, N,N-dihexadecyl-beta-alanine, N-nonadecyl-betaalanine, N-eicosyl-beta-alanine, N-docosyl-beta-alanine, N-pentacosyl-beta-alanine, N,N-dipentacosyl-bctaalanine and others. The salts of N-mono-alkyl-beta-alanines in which the alkyl group contains from 10 to l8 carbon atoms are particlularly preferred because of their superior emulsifying power and N-dodecyl-beta-alanine is the most proficient in this respect.

In the practice of this invention monomeric compounds or mixtures of monomers are polymerized in an aqueous medium containing a water-soluble salt of an N-alkyl-betaalanine and also containing, if desired, one or more other polymerization promoting materials.

The most essential class of polymerization promoting materials are the peroxygen catalysts, one or more of which is ordinarily used. Examples of such catalysts inelude hydrogen peroxide, benzoyl peroxide, o,o'-dichloro benzoyl peroxide, caproyl peroxide, caprylyl peroxide, pelargonyl peroxide, cumene monohydroperoxide, tertiary butyl monohydropcroxide, triisopropylbenzene monohydroperoxide, l-hydroxycyclohexyl monohydroperoxide, tertiary butyl diperphthalate, tertiary butyl perbenzoate, sodium, potassium and ammonium persulfate and others and combinations of these with reducing agents (in what is known as redox" catalysts) such as sodium sulfite. sugars, ferrous glueonate, various amines, and others both with and without small amounts of heavy metal salts such as ferrous and ferric sulfates, copper sulfate, cobalt chloride, potassium ferricyanide and the like. Still other polymerization promoting materials include electrolytes and buffers such as sodium and potassium pyrophosphates, potassium chloride, sodium bicarbonate, sodium carbonate, trisodium phosphate, sodium, potassium and ammonium hydroxide and others. Additional emulsifying agents may also be used, most effective of these being the fatty acid and rosin acid soaps, the hymolal sulfates and alkaryl sulfonates, the addition salts of long chain alkyl amines, and other ionic emulsifiers.

In carrying out the polymerization, an aqueous emulsion of monomeric material is first prepared using an emulsifier of this invention. The N-alkyl-beta-alanine may be neutralized by the addition of alkali or acid to form the emulsifying salt before addition to the aqueous medium but more conveniently the N-alkyl-betaalanine is added to the aqueous medium as such together with an appropriate quantity of neutralizing agent so that neutralization may occur in situ. The pH of the aqueous medium thus is conveniently adjusted by addition of a quantity of neutralizer calculated to yield the desired partial or complete neutralization of the N-alkyl-beta-alanine and in some cases, an excess of the neutralizer to yield a highly alkaline or highly acid reaction medium. After all the ingredients are added the reaction mixture is agitated and its temperature controlled by supplying a coolant or heating medium until polymerization proceeds to the desired degree and a stable aqueous dispersion of polymer is obtained. The temperature of polymerization is not critical and may vary from as low as 10 C. or lower to as high as 80 C. or higher.

The amount of the emulsifier of this invention needed for etficient emulsification and the production of stable polymeric dispersions will vary somewhat depending on the monomers polymerized and on the composition of the aqueous medium. For example, as little as 0.10 to 1.0% of a water-soluble salt of an N-alkyl-beta-alanine will yield a stable dispersion of a viuylidene chloride vinyl chloride copolymer. The incorporation of certain polymerization-promoting substances such as electrolytes and buffers sometimes makes necessary the utilization of slightly larger amounts of emulsifier. In general amounts of an emulsifier of this invention ranging from 0.10 to 15% by weight (as unneutralized N-alkyl-beta-alanine) are found satisfactory for most purposes when sufficient acid or alkaline neutralizing agents are utilized as to yield at least 0.1 to 10% of the water-soluble emulsifying salt.

The hydrogen ion concentration of the aqueous reaction medium has a profound effect on the reaction rate obtainable in aqueous emulsion polymerization with known emulsifiers. The N-alkyl-beta-alanines, however,

are useful over a very wide pH range with the obtainment of maximum reaction rates. For example, mixtures of butadiene with styrene and/or acrylonitrile have been polymerized to substantial completion at temperatures ranging from 5 to 40 C. in as little as 8 to 15 hours at a pH ranging from 1.5 or lower to 9.0 or higher. In general the pH of the reaction medium may vary from as low as 1.5 to as high as 11.5, depending on the other ingredients of the reaction medium, with obtainment of maximum reaction rates.

The method of this invention is applicable generally to the polymerization of monoolefinic unsaturated compounds polymcrizable in aqueous emulsion, particularly those containing the CHz=C group, that is, vinylidene comp unds containing a terminal methylene group atteched by a double bond to a carbon atom. Examples of arch compounds include viuylidene compounds containing only one carbon-to-carbon unsaturated bond such as vinyl chloride, viuylidene chloride, styrene, pchlorostyrene, 3.5-dichlorostyrene, p-methoxy styrene, the acrylic acids such as acrylic acid, methacrylic acid and their nitrilcs, esters and amides such as acrylonitrile, ll'i3ii'l :crylouitrile. alpha-chloro acrylonitrile, methyl acrylate, ethyl acrylate, methyl methacrylate, butyl ethacrylatc, mcthacrylamide, N,N-dimethyl acrylamide, vinyl esters such as vinyl acetate, vinyl propionate, vinyl licnzoatc and the like, vinyl methyl ketone, vinyl methyl ether, vinyl pyridine, vinyl carbazole, isobutylene, ethylcnc. and other similar monoolefinic polymerizable com pounds. The above viuylidene compounds may be copolymcrizcd with one another, in mixtures of two or more. or with one or more other unsaturated polymerizuble materials such as diethyl maleate, diethyl fumarate, mulcic acid or anl'lydridc and others.

It is to he understood from the above examples that vinyl compounds are a subgenus of viuylidene compounds since they contain the characteristic CH2% structure, one of the free valences being connected to hydrogen to form the (vinyl) The water-soluble salts of the N-alkyl-beta-alanines of this invention are particularly applicable to the polymerization of monomeric mixtures comprising a major proportion of a chloroethylcne containing from one to two chlorine atoms on one only of the carbon atoms and which have only hydrogen atoms on the remaining valences of the carbon atoms, that is, vinyl chloride and viuylidene chloride, mixtures of these materials and mixtures of one or both of these with lesser proportions of materials such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl alpha-chloro acrylate, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl bromide, vinyl fluoride, viuylidene bromide, viuylidene chlorofiuoride, and others.

Particularly useful aqueous polymeric dispersions are obtained with monomeric mixtures comprising from to by weight of viuylidene chloride, 5 to 15% vinyl chloride and 5 to 15 of an alkyl acrylate such as ethyl acrylate for the product in this case is a film-forming latex especially adapted as a fruit-dipping latex (antitranspirant coating), as a paper and textile coating and impregnating composition, and as a latex for the formation of air-dried unsupported film.

The invention will be described with reference to the following specific examples which are intended to be merely illustrative of the invention and not a limitation on the scope thereof.

Example 1 Material Sample (3 Sample I) Vinylideue chloride 15.4 15.4 Vinyl chloride 2. 3 2.3 Methyl aerylate. c 2.3 2.3 KzSgOs a D. l l). l N-dndeeyl beta alanine. 1.0 0. 75 Hydrochloric acid (IN) 3.9 In! I 2.9 ml. Water l 26. 0 7.0

1 Suilicicnt to neutralize 35.5% of Ndodeeylbeta-alaniue. 2 Su lficient to neutralize 26.4% of N-dodccyl-beta-nlanine. The reaction mixture in each case is maintained at 50 C. until zero pressure in the reaction vessel is obtained indicating substantially complete reaction (98 to 99% conversion). Sample C reacts to zero pressure in 9 hours and Sample D in about 12 hours producing in each case a stable aqueous polymeric dispersion or latex. Similar reactions employing lauryl amine hydrochloride or other quaternary ammonium salts of long chain alkyl amines as emulsifying agents require reaction periods of from 2 to 10 hours longer to reach completion. Samples of solid polymer from the latices of Samples C and D when heated in air for one hour at F. are superior in their heat resistance to polymers prepared in the presence of the quaternary ammonium alkyl amine salts as emulsifying agents.

in a similar fashion both anionic and cationic latices result from the polymerization in the presence of a salt of an Nalkyl-bcta-alaninc of monomeric mixtures containing butadiene and methyl methacrylatc, butadiene, styrene and vinyl pyridine, butadicne, acrylonitrile, and on olefinically unsaturated acid such as sorhic acid, acrylic acid, mcthacrylic acid and others, (1) styrene and acrylonitrile. (2) vinyl chloride, vinyl acetate and maleic acid.

(3) vinyl chloride, octyl acrylate, and vinyl benzoate, and (4) vinyl chloride alone. In each case the reaction rate is faster and the product is an aqueous dispersion or latex of improved stability over those obtainable with conventional anionic and cationic emulsifiers.

The latices produced by the method of this invention, such as those obtained in Example 1, are of considerable utility in dipping, coating and impregnating textiles, paper, leather, and related materials because of the unique aflinity and excellent wetting action on the fibers of the beta-alanine emulsifiers. Because it is possible to change the charge on the emulsifier by a change of pH, it is very easy to coagulate the polymeric latices when desired. In paper coating and impregnating the paper fibers usually carry a negative charge so that when a cationic latex or polymer dispersion made with an acid salt of an N-alkyl-beta-alanine is added to the beater or used in a skim-coating operation eflicient coagulation and distribution of the polymer about the fibers is obtained.

While I have disclosed certain preferred manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for the precise proportions of the materials utilized may be varied and equivalent chemical materials employed, if desired, without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In the process of manufacturing a stable synthetic polymer latex having affinity for fibrous materials such as textiles and paper and having any desired pH within the range of about 1.5 to 11.5 by the polymerization in aqueous emulsion of a monomeric material consisting essentially of from 75 to 90% by weight of vinylidene chloride, 5 to 15% by weight of vinyl chloride and 5 to 15% by weight of an alkyl acrylate, the steps which comprise forming an aqueous emulsion of said monomeric material with the emulsifying agent N-dodecyl-betaalanine, adding to the emulsion a suflicient quantity of a neutralizing agent selected from the class consisting of hydrochloric acid and alkali hydroxides to neutralize the N-dodecyl-beta-alanine and form the salt thereof and to produce the desired pH and then agitating the emulsion in the presence of a polymerization catalyst at a temperature of from C. to 80 C. to effect conversion of the monomeric material to polymer and thus produce a stable latex.

2. In the process of manufacturing a stable synthetic polymer latex having aflinity for fibrous materials such as textiles and paper and having any desired pH within the range of about 1.5 to 9 by the polymerization in aqueous emulsion of a monomeric material consisting essentially of from to 90% by weight of vinylidene chloride, 5 to 15% by weight of vinyl chloride and 5 to 15% by weight of an alkyl acrylate, the steps which comprise forming an emulsion of said monomeric material with from 0.1 to 10.0% of the emulsifying agent N- dodccyl-bcta alanine, adding to the emulsion a sufficient quantity of hydrochloric acid to neutralize the N-dodecylbeta-alanine and form the salt thereof and to produce the desired pH and then agitating the emulsion in the presence of a polymerization catalyst at a temperature of from 5 C. to 40 C. to effect substantially complete conversion of the monomeric material to polymer and thus produce a stable latex.

3. The process of claim 2 wherein the alkyl acrylate is methyl acrylate.

4. The process of claim 2 wherein the alkyl acrylate is ethyl acrylate.

5. In the process of manufacturing a stable synthetic polymer latex having aflinity for fibrous materials such as textiles and paper and having any desired pH within the range of about 1.5 to 11.5 by the polymerization in aqueous emulsion of monomers consisting essentially of monoolefinic unsaturated compounds containing the CH2=C group, the steps which comprise forming an emulsion of said monomeric material with the emulsifying agent N-dodecyl-beta-alanine, adding to the emulsion a sufficient quantity of a neutralizing agent selected from the class consisting of hydrochloric acid and alkali hydroxides to neutralize the N-dodecyl-beta-alanine and form the salt thereof and to produce the desired pH and then agitating the emulsion in the presence of a polymerization catalyst at a temperature of from -10 C. to C. to effect conversion of the monomeric material to polymer and thus produce a stable latex.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,012 Isbell Apr. 19, 1949 2,563,079 Smith Aug. 7, 1951 2,684,954 Miller July 27, 1954 

1. IN THE PROCESS OF MANUFACTURING A STABLE SYNTHETICPOLYMER LATEX HAVING AFFINITY FOR FIBROUS MATERILS SUCH AS TEXTILES AND PAPER AND HAVING ANY DESIRED PH WITHIN THE RANGE OF ABOUT 1.5 TO 11.5 BY THE POLMERIZATION IN AQUEOUS EMULSION OF A MONOMERIC MATERIAL CONSISTING ESSENTIALLY OF FROM 75 TO 90% BY WEIGHT OF VINYLIDENE CHLORIDE, 5 TO 15% BY WEIGHT OF VNYL CHLORIDE AND 5 TO 15% BY WEIGHT OF AN ALKYL ACRYLATE, THE STEPS WHICH COMPRISE FORMING AN AQUEOUS EMULSION OF SAID MONOMERIC MATERIAL WITH THE EMULSIFYING AGENT N-DODECYL-BETAALAMINE, ADDING TO THE EMULSION A SUFFICIENT QUANTITY OF A NEUTRALIZING AGENT SELECTED FROM THE CLASS CONSISTING OF HYDROCHLORIC ACID AND ALKALI HYDROXIDES TO NEUTRALIZE THE N-DODECYL-BETA-ALANINE AND FORM THE SALT THEREOF AND TO PRODUCE THE DESIRED PH AND THEN AGITATING THE EMULSION IN THE PRESENCE OF A POLYMERIZATION CATALYST AT A TEMPERATURE OF FROM -10*C. TO 80*C. TO EFFECT CONVERSION OF THE MONOMERIC MATERIAL TO POLYMER AND THUS PRODUCE A STABLE LATEX. 